Method for producing heterogeneous composites

ABSTRACT

A method for selecting materials and processing conditions to prepare a heterogeneous structure in situ via the reaction of a homogeneous mixture of a reactive organic compound and a filler, which may then optionally be sintered. The method is employed to provide a heterogeneous composite possessing exceptionally high thermal and/or electrically conductivities for a given concentration of conductive filler. The choice of materials as well as processing conditions employed, as will be described below, have a strong effect on the rate domain formation/heterogeneity of the structure formed, the extent of filler particle-particle interactions within filler-rich domains, and ultimately the thermal and/or electrical conductivity. Proper choice of these conditions can lead to composites having enhanced properties at a reduced bulk filler concentration.

CROSS REFERENCE

This application claims the benefit of, and incorporates by reference,U.S. Provisional Patent Application No. 60/896,961 filed on Mar. 26,2007 with the United States Patent and Trademark Office.

FIELD OF THE INVENTION

The present invention relates to a method for creating heterogeneouspolymer-filler composites in situ via a reaction of a homogeneousmixture of a filler and a reactive organic compound. The heterogeneousstructure comprises highly filler-rich areas whose concentration isgreater than that of the bulk filler concentration.

BACKGROUND OF THE INVENTION

Electrically conductive polymer composites often consist of electricallyinsulating polymers filled with electrically conductive fillers. Suchfillers often consist of metal- or carbon-based fillers often in theform of flake or fibers. In order to make the composite conductive, thefillers are added to the point a critical filler concentration isreached at which the composite changes from electrically insulating toelectrically conducting. This concentration, termed the percolationthreshold, is associated with a continuous electrical pathway formedfrom the touching or “percolation” of conductive filler particles.Beyond this threshold, the electrical conductivity can be furtherimproved by addition of filler to the polymer matrix. The ultimateconductivity beyond the threshold will depend on the type of filler usedand the maximum obtainable filler loading before tradeoffs in othercomposite properties becomes unacceptable from an application standpoint

Electrically conductive polymer composites are commonly used for suchapplications requiring electromagnetic shielding, electrostaticdischarge, or high conductivity for device interconnects or circuitry.The type of application will dictate the ultimate conductivity neededwhich will dictate the type and concentration of conductive fillers usedin the composite material. In many instances the level of fillerrequired leads to undesirable sacrifices in other important physicalcharacteristics of the composite, such as dispense viscosity, adhesion,impact strength, among other things. In some instances, the cost of thefiller is a limiting factor, particular for such fillers as gold,silver, or carbon fibers. It would be thus desirable to achieve highlevels of electrically conductivity with minimal loss in polymerattributes.

In the area of thermally conductive applications, surface mounting ofelectronic composites via interface adhesives is well developed inautomated package assembly systems. Such adhesives are used in severalapproaches to provide lid attach, sink attach and mainly thermaltransfer from flip chip devices, as well as against mechanical shock andvibration encountered in shipping and use. As semiconductor devicesoperate at higher speeds and at lower line widths, the thermal transferproperties of the adhesive are critical to device operation. The thermalinterface adhesive must create an efficient thermal pathway between thedie or lid and the heat sink as the adhesive itself due to interfaceresistance and bulk resistance is typically the most thermally resistantmaterial in the die-adhesive-lid-adhesive-sink or die-adhesive-sinkconfiguration. The thermal interface adhesive must also maintainefficient thermal transfer properties through reliability testing whichsimulates actual use conditions over the life of the device. Moreover, asuitable adhesive must have certain fluid handling characteristics, andexhibit specific adhesion, controlled shrinkage, and low corrosivity inorder to provide long term defect-free service over the thermaloperating range of the electronic circuit package.

As with traditional electrical applications mentioned above, interfaceadhesives having high bulk thermal conductivities are often made byadding large levels of thermally conductive filler to the reactiveorganic resin. In many instances, undesirable increases in viscosityoccur to the point handling (or dispensing) becomes an issue which oftenlimits the thermal conductivity that can be achieved. To help overcomethis issue, low molecular species, such as non-reactive solvent,plasticizer or other liquid viscosity reducing diluents are added to theformulation. However, a downside to this approach, as seen in epoxybased formulations, is these low molecular weight species causeshrinkage issues, void formation, and delamination when the adhesive iscured.

Other approaches for obtaining high bulk thermal conductivities haveemployed fillers that are known to sinter as temperatures amenable toelectrical devices processing temperatures. For example, U.S. Pat. No.7,083,850 entitled “Electrically Conductive Thermal Interface” describesa porous, flexible, resilient heat transfer material which comprises anetwork of metal flakes. The material is made by forming a conductivepaste comprising a volatile organic solvent and conductive metal flakes.The conductive paste is heated to a temperature below the melting pointof the metal flakes, thereby evaporating the solvent and sintering theflakes only at their edges. While highly thermally conductive, thismaterial is quite limited in its ability to adhere to surfaces and hasan intrinsically high modulus owing to pure filler remaining once thesolvent is removed. Moreover, most packaging processes prefer low solverto solvent-less materials owing to the complexities and environmentconcerns with removing solvent.

It would thus be desirable to sinter metal flakes within interfacematerial obtaining adhesive. Unfortunately, sintering in not achieved atlow to moderate fillers loadings. This limitation is associated with thelack of direct filler particle contacts required for filler to occur dueto the matrix material that coats them. It is only at very high volumepercent filler that some sintering occurs, but at such concentrationsthe unreacted adhesive composition becomes extremely viscous and evensolid-like and lacks the desirable polymeric attributes such as goodadhesion, toughness, etc. It is this reason that existing approacheshave resorted to using considerable amounts of solvents to address theviscosity issue which again has its downsides as mentioned earlier.

To this end, it would be desirable to provide a solvent-free (or lowsolvent) adhesive composition comprising a matrix polymer and low tomoderate levels of filler material which exhibits high conductivityresulting from sintered filler, and also provides adhesive propertieswhile maintaining beneficial properties such as dispensability, propercoefficient of thermal expansion, improved toughness, shock andvibration resistance, environmental protection, and the like.

It is further desirable to provide a homogeneous material in theunreacted state comprising filler particles in a reactive organic matrixwhose properties and cure condition could be controlled to generate aheterogeneous structure during curing and whose final properties exhibithigh levels of thermal and/or electrical conductivity among otherattributes.

SUMMARY OF THE INVENTION

This invention describes a method for selecting materials and processingconditions to prepare a heterogeneous structure in situ via the reactionof a homogeneous mixture of a reactive organic compound and a filler,which may then optionally be sintered. In a preferred embodiment of thepresent invention, the method is employed to provide a heterogeneouscomposite possessing exceptionally high thermal and/or electricallyconductivities for a given concentration of conductive filler. Thechoice of materials as well as processing conditions employed, as willbe described below, have a strong effect on the rate domainformation/heterogeneity of the structure formed, the extent of fillerparticle-particle interactions within filler-rich domains, andultimately the thermal and/or electrical conductivity. Proper choice ofthese conditions can lead to composites having enhanced properties at areduced bulk filler concentration.

One aspect of the present invention is lower electrical percolationthreshold concentrations and enhanced conductivities beyond percolationcan be achieved through the formation of a heterogeneous composite fromthe reaction of a homogeneous mixture of filler and organic compound.Through appropriate selection and reaction of the organic compound, aheterogeneous structure can be formed comprising filler rich domainsthat are greater in concentration that of the bulk filler concentration.Such a structure, as will be shown, ultimately allows for electricallypercolation to occur at significantly lower concentrations of fillerthan what is required in final composites that comprise a homogeneousdispersion of filler. Moreover, the structure when formed fromsinterable or metal fillers and cured under the appropriate conditionsis capable of forming a fused network of filler thereby furtherimproving electrical conductivity at levels.

In a first aspect of the present invention, a method for producing acomposite is provided comprising a) selecting a reactive organiccompound, b) selecting an inorganic filler component, c) mixing thereactive organic compound and the inorganic filler component, wherein atroom temperature the organic compound and the filler component mix toform a substantially homogeneous structure having a bulk fillerconcentration, and d) reacting the organic compound to form a polymer,wherein the polymer has a repulsive interaction with the inorganicfiller thereby creating, in situ, a heterogeneous structure comprisingfiller rich domains.

In one embodiment of the present invention, the concentration of thefiller is higher than that of a bulk filler concentration. In a furtherembodiment of the present invention, the reactive organic compoundcomprises at least one of monomers, oligomers, prepolymers, or reactivepolymers. In a further embodiment of the present invention, the organiccompound further comprises a cure agent. In another embodiment of thepresent invention, the reaction of step d) is advanced by heating themixture. In an alternate embodiment of the present invention, thereaction of step d) is advanced by exposing the mixture to activatingultraviolet radiation.

In yet another embodiment of the present invention, the compositionfurther comprises a second filler component. In an additional embodimentof the present invention, the second filler component residessubstantially with the polymer after the organic compound has beenreacted.

In a further embodiment of the present invention, the inorganic fillercomponent comprises an inorganic filler coated with an organic coating.In another embodiment of the present invention, the organic coating onthe filler has an affinity for the reactive organic compound. In apreferred embodiment of the present invention, the coating on the fillercomprises stearic acid. In another embodiment of the present invention,the coating on the filler is present in a single layer as averaged oversubstantially all of the filler. In yet another embodiment of thepresent invention, the coating on the filler has a repulsive interactionwith the new polymer formed from the step of reacting the organiccomponent. In a preferred embodiment of the present invention, thecoating on the filler comprises a non-polar coating and the polymerformed during step d) comprises polar moieties.

In another embodiment of the present invention, the filler is thermallyconductive and/or electrically conductive. In an additional embodimentof the present invention, the filler comprises solder. In a furtherembodiment of the present invention, the filler comprises less than 75percent by weight based on the total weight of the composition. In astill further embodiment of the present invention, the filler comprisesless than 50 percent by volume based on the total volume of thecomposition. In one embodiment of the present invention, the fillercomprises at metallic filler of at least one of nickel, copper, silver,palladium, platinum, gold, and alloys thereof. In a further embodimentof the present invention, the filler comprises a cold worked silverflake.

In a further aspect of the present invention, the filler comprises asinterable filler. In one embodiment of the present invention, themethod further comprises the step of sintering the filler particlestogether. In another embodiment of the present invention, the step ofsintering the filler particles together and the step of reacting theorganic compound are performed simultaneously. In still anotherembodiment of the present invention, substantially all of the sinterablefiller particles that are in direct contact with one another aresintered. In one embodiment of the present invention, the step ofsintering is performed at a temperature above approximately 100° C. Inanother embodiment of the present invention, the step of sintering isperformed at a temperature of above approximately 150° C. In a stillfurther embodiment of the present invention, the sintering step isenhanced by an applied pressure on the composition. In anotherembodiment of the present invention, the degree of sintering isregulated through selection of sintering temperature and pressure. In astill further embodiment of the present invention, the mixture of thereactive organic component and the filler is a solvent-free 100% solidscomposition.

In a further aspect of the present invention, a composite material isprovided comprising, an organic compound, and, an inorganic filler,wherein the organic compound and inorganic filler comprise aheterogeneous structure comprising filler-rich domains wherein thefiller concentration is higher than the bulk filler concentration, andsaid filler rich domains were formed in situ from a homogeneous mixtureof the organic compound and the inorganic filler.

In a still further aspect of the present invention, a method forincreasing the conductivity of a conductive composition is providedcomprising, selecting an inorganic filler which is at least one ofthermally conductive and electrically conductive, selecting an organicmaterial, selecting a desired filler amount, mixing the conductivefiller and organic material, wherein the homogeneous mixture of fillerand matrix material comprises a bulk conductivity, and selecting cureconditions to create a heterogeneous structure so as to provide a curedcomposition comprising a conductivity that is higher than the bulkconductivity of the mixture having a homogeneous structure.

In an additional aspect of the present invention, a thermally conductiveadhesive is provided comprising, a filler coated with a non-polarcoating, an organic component comprising polar functionality, andwherein the thermal conductivity of the cured adhesive is greater than15 W/mK and the silver flake concentration is less than 50% by volume.Unlike other methods for producing filled polymeric systems, the methodsof embodiments of the present invention provide higher thermal and/orelectrical conductivity at significantly lower filler contents. Thistypically leads to lower viscosities, better toughness, better adhesion,and other enhanced physical properties all while achieving higherconductivities that bulk filler loading would allow.

Additionally, the lower concentration of filler permits less adsorbedmoisture and air in the formulation brought in by the filler allows forbetter wetting of a substrate, and enables for application methods suchas screen printing due to the newly achieved low-viscosity 100% solidssystem, which provides the same or better conductivity as prior artsystems.

As will be realized by those of skill in the art, many differentembodiments of the methods for producing a heterogeneous composite fromthe reaction of homogeneous organic compound-filler mixture according tothe present invention are possible. Additional uses, objects,advantages, and novel features of the invention are set forth in thedetailed description that follows and will become more apparent to thoseskilled in the art upon examination of the following or by practice ofthe invention.

Thus, there has been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thatfollows may be better understood and in order that the presentcontribution to the art may be better appreciated. There are, obviously,additional features of the invention that will be described hereinafterand which will form the subject matter of the claims appended hereto. Inthis respect, before explaining several embodiments of the invention indetail, it is to be understood that the invention is not limited in itsapplication to the details and construction and to the arrangement ofthe components set forth in the following description or illustrated inthe drawings. The invention is capable of other embodiments and of beingpracticed and carried out in various ways.

It is also to be understood that the phraseology and terminology hereinare for the purposes of description and should not be regarded aslimiting in any respect. Those skilled in the art will appreciate theconcepts upon which this disclosure is based and that it may readily beutilized as the basis for designating other structures, methods andsystems for carrying out the several purposes of this development. It isimportant that the claims be regarded as including such equivalentconstructions insofar as they do not depart from the spirit and scope ofthe present invention.

So that the manner in which the above-recited features, advantages andobjects of the invention, as well as others which will become moreapparent, are obtained and can be understood in detail, a moreparticular description of the invention briefly summarized above may behad by reference to the embodiment thereof which is illustrated in theappended drawings, which drawings form a part of the specification andwherein like characters of reference designate like parts throughout theseveral views. It is to be noted, however, that the appended drawingsillustrate only preferred and alternative embodiments of the inventionand are, therefore, not to be considered limiting of its scope, as theinvention may admit to additional equally effective embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A scanning electron micrograph (SEM) photomicrograph of aheterogeneous composite according to an embodiment of the presentinvention. Note the sample because of its high electrical conductivityrequired no gold sputter coating prior to SEM imaging.

FIG. 2 A SEM photomicrograph of a homogeneous composite according toconventional technologies. Note the sample because of its limitedelectrical conductivity required gold sputter coating prior to SEMimaging.

FIG. 3 A SEM photomicrograph of a homogeneous composite according toconventional technologies. Note the sample because of its limitedelectrical conductivity required gold sputter coating prior to SEMimaging.

FIG. 4 A graph illustrating the effect of silver flake concentration onthe thermal conductivity of composites based on homogeneous structureversus heterogeneous structure (derived in situ).

FIG. 5 A graph illustrating the effect of silver flake concentration onthe electrical volume conductivity of composites based on homogeneousstructure versus heterogeneous structure (derived in situ).

FIG. 6 A SEM photomicrograph of a heterogeneous composite in anembodiment of the present invention containing 5 volume percent silverflake. Note: this image was taken at one half the magnification of FIGS.1-3.

FIG. 7 A graph illustrating the effect of cure temperature on thethermal conductivity of pure silver flake (squares—left axis) andheterogeneous composites according to an embodiment of the presentinvention (circles—right axis).

FIG. 8( a) A SEM photomicrograph of pure silver flake at 25° C.

FIG. 8( b) A SEM photomicrograph of pure silver flake heated at 200° C.

FIG. 9 A graph illustrating the effect of cure temperature on the volumeelectrical conductivity of heterogeneous composites containing 33 volumepercent silver flake according to an embodiment of the presentinvention.

FIG. 10 A SEM photomicrograph showing a heterogeneous structuregenerated during the Michael's addition reaction between ethoxylatedbisphenol A diacrylate and PAA cured at 200° C. (33 volume percent Agflake filled) in an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a first embodiment of the present invention a method is presented forproducing a heterogeneous structure in situ via the reaction of ahomogeneous mixture of a filler and reactive organic compound. Themechanism of structure formation is achieved through the properselection of component materials and adherence to particular processingconditions. In one embodiment of the present invention, the fillercomponent comprises a conductive filler (thermal, electrical or both)and the organic compound comprises a monomer and optionally a curativeagent. The formation of filler rich domains during reaction of theorganic material allows for direct filler-to-filler particle contacts tobe made. In the presence of heat the particles may further sintertogether. Sintering eliminates the contact resistance between thepreviously non-sintered filler particles thereby substantially improvingthe thermal and/or electrically conductivity of the composite.

While not fully understood and not wishing to be bound by this theory,it is believed that domain formation and sintering in the compositionare sensitive to the organic material's cure temperature, the cure time,and the level of pressure applied during the cure. In other words,domain formation and sintering are kinetically driven processes. In astill a further embodiment, the rate at which the sample is heated willaffect the extent of domain formation and sintering. The effects of curetime, temperature, and pressure are outlined in the exemplaryembodiments discussed herein. In total, the processing conditions can betailored to achieve a conductive adhesive having the best combination ofproperties at minimal filler loading, which often translates to lowercost and opportunity to take advantage other properties that areadversely affected by high filler loadings. In some cases, when theadhesive is employed in an application that is not able to withstandhigh sintering temperatures, higher pressures or non-traditionalsintering techniques may used to achieve exceptionally highconductivities.

The filler component and reactive organic compounds are chosen so as tocreate a homogeneous mixture when mixed. However, during the cure, it isbelieved that the resulting polymer formed from the organic compoundthen has a repulsive interaction with the filler so as to form aheterogeneous compound having filler-rich domains wherein the fillercomposition is significantly higher than the bulk filler concentration.Thus, while the overall (bulk) filler concentration of the compound doesnot change, the filler particles and the organic component separate insitu into respective regions of high concentration. This phenomenon canlead to a network of interconnected filler particles formed in situ froma mixture having very few, if any, initial filler-filler contacts.

There are several approaches which may be employed to create therepulsive interaction between the filler component and the organiccompound. However, in a preferred embodiment of the present invention,this is achieved by coating a metallic filler particle with a non-polarcoating and mixing the coated filler in a reactive organic compoundcomprising a relatively non-polar resin and a polar curing agent. In anuncured state, the resin, curative, and filler form a relativelyhomogeneous mixture in which the coated filler and the resin arecompatible with one another and form a relatively homogeneous mixture.However, with the application of heat the curing agent reacts with theresin forming a polymer having polar moieties thereon, resulting in arepulsive interaction between the non-polar coating on the filler andthe polar moieties on the polymer. This leads to the gross separation ofthe two materials to create polymer-rich and filler-rich domains whoserespective concentrations are significantly higher than the bulkconcentrations of polymer and filler, respectively. Moreover, extensivedomain formation is capable of creating continuous filler-rich domainswith substantial particle to particle contact between most of the fillerparticles.

Other types of interactions capable of creating repulsive effects uponcuring of the organic compound in the presence of the filler, couldconsist of, but are not limited to, electrostatic interactions, hydrogenbonding interaction, dipole-dipole interactions, induced dipoleinteraction, hydrophobic-hydrophilic interactions, van der Waalsinteractions, and metallic interactions (as with an organometalliccompound and metallic filler). Other forms of repulsive interactionscould arise from entropic related effects such as molecular weightdifferences in the polymers formed from the organic compound(s).Additionally, repulsive interactions could arise as a result of anexternal stimulus such as electrical field.

The domains formed upon curing of the organic compound in the presenceof the filler results in filler-rich domains having a higher than bulk(average) filler concentrations and in organic rich domains having lowerthan bulk (average) filler concentrations. The areas of higher thanaverage filler concentration can form semi-continuous or continuouspathways of conductive filler material extending throughout the body ofthe cured composition. These pathways provide a low resistance routethrough which electrons and/or thermal phonons can travel. In otherwords, the pathways or channels allow for greatly enhanced thermal orelectrical conductivity. This conductive pathway may be further enhancedby sintering the filler particles together.

Sintering, as it is understood in the art, is a surface meltingphenomenon in which particles are fused together at temperatures belowthe material's bulk melting temperature. This behavior is brought aboutby a tendency of the material to relax into a lower energy state. Assuch, selection of filler type, size, and shape can greatly affect thesinterability of the filler particles. Certain particles, such as thin,wide, flat, plates are often formed by shearing large particles viavarious milling processes. This process imparts a large amount ofinternal stress in addition to creating a large amount of surface area.When a certain amount of heat is added to the particles, they will havethe tendency melt and fuse together thereby relieving the internalstrain and decreasing the overall surface energy of the particles. Forthis reason, the preferred filler particles for use in the presentinvention are those that comprise some degree of thermal or electricalconductivity and sinter easily. In a still further embodiment of thepresent invention, the preferred filler comprises a metallic particlethat has been subjected to cold working which has imparted strain intothe structure of the filler.

The sintering temperature will vary according to the material chosen asthe filler, as well as the geometry of the filler particle. However, ina preferred embodiment of the present invention, it is advantageous tobalance the cure of the organic compound and the sintering of the fillersuch that they occur simultaneously. In this embodiment, the curetemperature and profile is selected to coincide with the sinteringtemperature of the filler, so as the organic compound becomes repulsiveto the filler and the filler particles are forced together, theindividual filler particles can sinter once particle to particle contactis made. This is believed to be responsible for the continuous fillerstructure seen throughout the fully cured composition. In a preferredembodiment of the present invention, the cure temperature is at leastabout 100° C., more preferably about 150° C., and even more preferablyabove 150° C. for a silver flake filler.

In a preferred embodiment of the present invention, the compositions arecured and optionally sintered via application of heat to thecomposition. This is commonly accomplished in a cure oven whereby hotair or radiated heat is used to increase the temperature of thecomposition. In alternate embodiments of the present invention, othermethods of cure may be employed such as induction curing in anelectromagnetic field, microwave curing, infrared curing, electron beamcuring, and ultraviolet curing. Additionally, the cure reaction may beself accelerated through the use of an exothermic cure reaction. Anon-thermal cure may be desirable, for example, when the composition iscoated on a temperature sensitive substrate such as a plastic.

In one embodiment of the present invention the filler comprisesinorganic fillers. Available fillers include pure metals such asaluminum, iron, cobalt, nickel, copper, zinc, palladium, silver,cadmium, indium, tin, antimony, platinum, gold, titanium, lead, andtungsten, metal oxides and ceramics such as aluminum oxide, aluminumnitride, silicon nitride, boron nitride, silicon carbide, zinc oxide.Carbon containing fillers could consist of graphite, carbon black,carbon nanotubes, and carbon fibers. Suitable fillers additionallycomprise alloys and combinations of the aforementioned fillers.Additional fillers include inorganic oxide powders such as fused silicapowder, alumina and titanium oxides, and nitrates of aluminum, titanium,silicon, and tungsten. The particulate materials include versions havingparticle dimensions in the range of a few nanometers to tens of microns.In a preferred embodiment of the present invention, the filler comprisesa material that is either thermally conductive, electrically conductiveor both. Although metals and metal alloys are preferred for use inseveral embodiments of the present invention, the filler may comprise aconductive sinterable non-metallic material.

In an embodiment of the present invention, the filler component must beable to interact with the organic compound to impart a heterogeneousstructure in the finished material. In a preferred embodiment of thepresent invention as discussed above, this is accomplished through theinteraction of a polar organic compound with a non-polar filler. Forpreferred filler materials, such as metals, the filler is coated with amaterial comprising the desired degree of polarity. In one preferredembodiment of the present invention, the filler coating comprises anon-polar fatty acid coating, such as stearic acid. In a still furtherembodiment of the present invention, the filler coating comprisesanother non-polar material, such as an alkane, paraffin, saturated orunsaturated fatty acid, alkene, fatty esters, or waxy coating. Inadditional embodiments of the present invention, non-polar coatingscomprise ogranotitanates with hydrophobic tails or silicon basedcoatings such as silanes containing hydrophobic tails or functionalsilicones.

In an alternate embodiment of the present invention, the polarity of thefiller/coating and polymer are reversed wherein the filler/coatingcomprises a polar moiety and the organic compound comprises a non-polarpolymer. Similarly, in an embodiment of the present invention, in whicha repulsive effect other than polarity is employed to drive the in situdomain formation, the active properties of the filler and organiccomponents may be interchanged.

In a preferred embodiment of the present invention the organic compoundcomprises an epoxy resin and a cure agent. In this embodiment, theorganic compound comprises from about 60 to about 100 volume percent ofthe total composition. In this embodiment, the organic compoundcomprises approximately from 70 to 80 percent by weight of a diglycidalether of a bisphenol compound, such as bisphenol F, and 20 to 30 percentby weight of a cure agent, such as a polyamine anhydride adduct.

In additional embodiments of the present invention, suitable organiccompounds comprise polysiloxanes, phenolics, novolac resins,polyacrylates, polyurethanes, polyimides, polyesters, maleimide resins,cyanate esters, polyimides, polyureas, cyanoacrylates, and combinationsthereof. The cure chemistry would be dependant on the polymer or resinutilized in the organic compound. For example, a siloxane matrix cancomprise an addition reaction curable matrix, a condensation reactioncurable matrix, a peroxide reaction curable matrix, or a combinationthereof. Selection of the cure agent is dependant upon the selection offiller component and processing conditions as outlined herein to providea heterogeneous structure formed in situ.

EXAMPLE 1

Silver flake coated with stearic acid was first added to a reactiveorganic resin, namely diglycidal either of bisphenol F (DGEBF), in a 100gram Hauschild® mixing cup and thoroughly mixed for a minimum of twocycles at 2200 rpm for 1 minute/cycle. A second reactive organiccompound, i.e. a curing agent, was then added and mixed for a minimum oftwo cycles at 2200 rpm for 1 minute/cycle. The resulting material wascast between 19 mm thick, Teflon coated aluminum plates separated with 1mm glass slides. Samples were cured with a convection oven using aprogrammed ramp which consisted of heating the sample from roomtemperature to 160° C. over the course of 40 minutes followed by anisothermal hold for 1 hour.

Bulk thermal conductivity was measured via the Flash Method (ASTME1461). Test specimens were cut from the cured samples. Samples were12.7 mm in diameter and ˜1 mm in thickness. All samples werespray-coated with a thin film of graphite to ensure complete absorptionof the incident radiation.

Volume electrical conductivity was measured as follows: Uncured sampleswere made into strips ˜1 mm in thickness, ˜40 mm in length, and ˜2 mm inwidth. Copper wire was placed at the ends of the uncured composite priorto curing. The ends of the wire were lightly sanded prior to insertion.The samples were cured using the same heating profile described above.The electrical resistance (or conductance) was measured using a Keithley580 Micro-ohmmeter. The volume conductivity was calculated from thesample dimensions and the measured resistance.

The morphology of the cured composites was analyzed via ScanningElectron Microscopy (SEM) using a FEI XL30 SEM set at an operatingvoltage of 10 kV and a spot size of 3. Highly electrically conductivesamples required no gold sputter coating, i.e. Example 1, whereas poorlyconductive samples did, i.e. Control 1-A and 1-B. Gold was applied underan Argon atmosphere, a pressure of ˜50-75 mTorr, and deposition time of20-30 s using a Denton Desk II sputter coater.

Table 1 lists three different composites ultimately differing instructure and corresponding conductivity. Choice of curative incombination with the other constituents (epoxy resin, filler and fillercoating) and curing conditions will dictate the structure formed duringcuring and the resulting properties of the composite. Example 1 in Table1 and the corresponding SEM photomicrograph shown in FIG. 1 illustratethat by using a polyamine anhydride adduct (PAA) to cure DGEBF in thepresence of stearic acid coated silver flake, a heterogeneous compositecan be formed during cure and thereby result in exceptional thermal andelectrical conductivity.

In the uncured state, Example 1 consists of homogeneous mixture ofDGEBF, PAA, and stearic acid coated silver. During cure, it is believedthat the resin and curative react to form a polymer that has a repulsiveinteraction between the newly-formed polymer and the stearic acid coatedsilver flake. The extent of repulsion is large enough that the polymermolecules would prefer to reside with other polymer molecules ratherthan with the stearic acid coated filler. Thus, the polymer diffuses toisolated domains thereby creating a highly heterogeneous structure ofpolymer-rich and silver-rich domains.

FIG. 1 is an SEM photomicrograph of the heterogeneous morphologyconsisting of discrete polymer-rich domains (very light, globularregions typically 5-20 microns in size) distributed throughout acontinuous silver-rich phase. (Note that the Example 1 sample in FIG. 1was not coated with gold prior to SEM imaging. Thus regions that areelectrically insulating will be heavily charged under the microscope andappear very bright and amorphous, i.e. polymer rich domains. Regionsthat are highly conductive will help dissipate the incident electronbeam and appear less charged and have finer detail, i.e. silver richdomain.) The silver rich regions comprise silver flake particles withdefine edges and shapes, unlike the polymer rich areas.

In contrast to Example 1, Control 1-A and Control 1-B samples based ondiethylentriamine (DETA) and an imidazole curative, respectively, andconsist of a cured composite that has a homogeneous structure comprisingan even distribution of silver throughout the sample as seen in FIGS. 2and 3. (Note; FIGS. 1-3 were all taken at the same magnification.) Inthis type of homogeneous structure, the local concentration of silver iscomparable to that of the bulk concentration, which is not the case inthe heterogeneous composites (Example 1).

Ultimately, the differences in structure formed upon cure lead todramatic differences in thermal and electrical properties. Theheterogeneous structure of Example 1 results in approximately 22 timesthe thermal conductivity and ˜3-4 orders of magnitude higher electricalconductivity than that of the homogeneous structure of Control 1-A and1-B samples.

TABLE 1 Effect of composite structure on the morphology and propertiesof silver flake filled - diglycidal either of bisphenol F (DGEBF)composites. Ingredient by wt % (vol %) Example 1 Control 1-A Control 1-BDGEBF 13.4 18.2 17.8 PAA^((a))  4.6 — — DETA^((b)) —  2.2 —Imidazole^((c)) — —  0.7 Silver flake^((d)) 82.0 79.6 81.5 (33 vol %)(30 vol %) (33 vol %) Total 100   100   100   Cured StructureHeterogeneous Homogeneous Homogeneous Thermal 22.3  0.92  1.2Conductivity, k (W/m · K) Electrical Volume 3.8E+04 3.2E+00 4.6E+01Conductivity, (S/cm) ^((a))Epoxy curative - PAA—polyamine anhydrideadduct formed from the reaction of diethylene triamine (DETA) andpthalic anhydride ^((b))Epoxy curative - DETA—diethylene triamine^((c))Epoxy curative - 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole(d)Stearic acid coated silver flake (surface area = 0.83 m²/g, weightloss in air at 538° C. = 0.35%)

EXAMPLE 2

The samples corresponding to data shown in Table 2 and FIGS. 4-6 wereprepared according the description provided in Example 1 with theexceptions of select electrical volume conductivity measurements. Theresistance (or conductance) of each sample dictated the choice ofresistivity instrumentation. Samples having resistances in excess of˜10¹⁰ ohms were measured via ASTM D-257 using a HP 4339B High ResistanceMeter equipped with a 16008B resistance cell. Samples were in the formof circular disks ˜1 mm in thickness and >60 mm in diameter. Sampleshaving resistances in the range of ˜10²-10¹⁰ ohms were measured using aKeithley 610C Electrometer. Samples in this case were in the form ofwell-defined strips. Uncured samples were cured into strips 1 mm inthickness, ˜40 mm in length, and ˜2 mm in width. Copper wire was placedat the ends of the sample prior to curing. The ends of the wire werelightly sanded prior to insertion. The samples were cured using the sameheating profile described in Example 1. The volume conductivity wascalculated from the sample dimensions and the measured resistance.Samples having electrical resistances below ˜10² ohms were measuredaccording the procedure described in Example 1.

Table 2 and FIGS. 4 & 5 show the effect of stearic acid coated silverflake concentration on the thermal and electrical conductivity of curedcomposites possessing a heterogeneous structure versus a homogeneousstructure (structures previously described in Example 1). Theheterogeneous structure in this example was formed from the reaction twoorganic components, namely DGEBF (resin) and PAA (curative) in thepresence of the stearic acid coated silver flake. As seen in FIG. 4, thethermal conductivity of the heterogeneous structure dramaticallyincreases with silver flake concentration. At about 33 volume percentsilver flake the thermal conductivity of the heterogeneous composite isroughly 100 times that of the unfilled polymer.

In contrast, when the DETA curative is used a homogeneous structure isformed and the thermal conductivity follows a much more shallow responsewith respect to filler loading. At about 33 volume percent silver flakethe thermal conductivity of the homogeneous material is only roughly 4times that of the unfilled polymer.

Comparing the two systems at a fixed thermal conductivity of 1 W/mK, theheterogeneous composite requires only about 5 volume percent silverflake whereas the homogeneous composite requires 7 times theconcentration of silver, i.e. about 35 volume percent to achieve thesame thermal conductivity. As will be discussed in Example 3, theexceptional thermal conductivity observed in the heterogeneous compositeis a result of the segregation of the polymerized material from thesilver particles which enables direct particle-particle contacts andsubsequent particle sintering.

In the case of electrical conductivity, the heterogeneous structureenables electrical percolation, i.e. the point at which the materialabruptly changes from electrically insulating to conducting, to beachieved at a fraction of the silver concentration needed to do the samein the homogeneous system. This observation is evident in the data shownin Table 2 and FIG. 5. The percolation threshold is about 3 volumepercent stearic acid coated silver flake in the heterogeneous composite(based on DGEBF and PAA) versus roughly 27 volume percent stearic acidcoated silver flake in the homogeneous composite (based on DGEBF andDETA). This much lower threshold is a result of creation of continuous,concentrated domains of silver upon curing. FIG. 6 shows suchmorphological features observed at 5 volume percent Ag Flake, i.e. justbeyond the electrical percolation threshold.

In addition to electrical percolation, the ultimate electricalconductivity is considerably higher at silver concentrations beyond thepercolation threshold. For example, the concentration of coated silverflake needed to achieve a volume conductivity of about 100 S/cm isroughly 4 volume percent for the heterogeneous composite whereas over 40volume percent silver flake is required for the homogeneous system. Aswill be discussed in Example 3, the exceptional thermal conductivityobserved in the heterogeneous composite is a result of the segregationof the polymerized material from the silver particles which enablesdirect particle-particle contacts and subsequent particle sintering.

TABLE 2 The effect of composite morphology on the thermal and electricalconductivity as function of silver flake concentration. ThermalElectrical Volume Vol % Silver Conductivity, k Conductivity, Flake (W/m· K) (S/cm) DETA Cured^((a)) 0 0.22 2.4E−15 5 0.31 8.4E−16 15 0.673.2E−14 20 0.69 1.4E−13 25 0.69 3.3E−14 30 0.92 3.2E+00 40 1.23 3.5E+01PAA Cured^((b)) 0.0 0.23 9.1E−16 1.0 0.21 4.8E−16 2.5 0.32 5.2E−15 4.00.44 1.6E+02 5 1.07 5.0E+02 10 2.82 4.3E+03 15 7.94 1.1E+04 20 9.101.7E+04 33.1 22.3 3.8E+04 ^((a))DETA—diethylene triamine used to cureDEGBF resin. ^((B))PAA—polyamine anhydride adduct used to cure DEGBFresin.

EXAMPLE 3

DGEBF (resin), PAA (curative), and stearic acid coated silver flake(filler) were mixed (uncured state) and characterized (cured state) asoutlined in Example 1. The samples were cured by placing them in apreheated convection oven and curing them for 2 hours. Studies onas-received flake involved first pressing the powder in to 1-3 mm thick,12.5 mm diameter pellet using a KBr hand press, set at a compressiveforce of approximately 0.5 Mg. The pellets were heat treated under thesame conditions at which the composites were cured in the previousexample.

Table 3 and FIG. 7 show how temperature dramatically affects the thermalconductivity of both the pure Ag flake and composites thereof. For bothmaterials, the higher cure temperatures result in higher conductivities.Interestingly, both sets of data possess the same sigmoidal shape (seeFIG. 7) with a small increase in conductivity observed below 120° C.,followed by a steep temperature increase in the vicinity of 160° C., andthen a plateau effect at about 200° C. and above. Similar to thecomposite, a 14 fold increase in conductivity is observed between thesilver flake at room temperature versus the flake heat treated at 200°C. The dramatic increase both sets of samples is a result of sinteringof the silver flake. Sintering of the particles eliminates the contactresistance between particles by creating a continuous pathway throughwhich thermal phonons (and electrons) can travel.

FIG. 8 provides morphological evidence of the sintering of silver in thepure silver flake and heterogeneous composite based on the same flake.The unsintered silver flake as shown in FIG. 8( a) comprises plate-likeparticles with sharp, well-defined edges. Heat treating the flakes tomoderate temperatures, i.e. 200° C. in the case of FIG. 8( b), causesthe flakes to sinter, ultimately forming a stable interconnectedstructure. In the case of the heterogeneous composite based on coatedsilver flake, DGEBF, and PAA, sintering is enabled by the formation ofthe silver rich domains. Extensive silver domain formation during curingcauses direct silver particle-to-particle contacts to occur. In thepresence of sufficient heat, these contacting particles will sinter.This ultimately creates interconnected network of silver particlesthereby minimizing the resistance to heat transfer.

As with thermal conductivity, electrical conductivity of theheterogeneous composite increases with cure temperature. The dataprovided in Table 3 and displayed in FIG. 9 show approximately a fourfold improvement in electrical conductivity when curing the 33 volumepercent coated silver/DGEBF/PAA sample at 200° C. as compared to 80° C.

TABLE 3 Effect of cure temperature on the thermal and/or electricalconductivity of pure Ag flake and Ag flake filled DGEBF cured with PAA.Thermal Conductivity, k Electrical Volume Sample Cure (W/m · K)Conductivity, (S/cm) Temperature 100% Ag 33% Ag Flake Filled 33% AgFlake Filled (° C.) Flake Composite Composite 25  11.3 1.3^((a)) — 80 —2.0 1.1E+04 120  37.9 8.6 2.1E+04 160 136.5 16.1 3.8E+04 200 154.0 24.84.4E+04 240 — 26.0 ^((a))Uncured sample.

EXAMPLE 4

Steric acid coated silver flake was first added reactive organic resin,namely DGEBF, in a 100 gram Hauschild® mixing cup and thoroughly mixedfor a minimum of two cycles at 2200 rpm for 1 minute/cycle. A secondreactive organic component, i.e. a curing agent (PAA), was then addedand mixed for a minimum of two cycles at 2200 rpm for 1 minute/cycle.The resulting material was cast between 19 mm thick, Teflon coatedaluminum plates separated with 1 mm glass slides as spacers. Sampleswere cured in a two stage process: (1) samples were placed in convectionoven and heated room temp to 120° C. (approximately 40° C./min ramp) andheld at 120° C. with a total heating time=2 hours (2) post-cure sampleswere placed in a preheated compression mold set at 200° C. for 1 hrunder various applied pressures. The resulting thermal conductivities ofthe samples were measured via the Flash Method.

TABLE 4 Effect of pressure on the thermal conductivity of in situderived, heterogeneous composites. Applied Pressure ThermalConductivity, k (psi) (W/m · K) 0 23.4 500 29.8

It is well known in the metallurgical literature, that the sintering ofmetal powders is facilitated by pressure. Thus, it was interest todetermine how pressure affects the thermal conductivity of aheterogeneous composite comprised of sinterable fillers, like that ofsilver. Table 4 shows that indeed exposing the composites to temperatureand pressure leads to higher conductivity.

EXAMPLE 5

Samples in Tables 5 and 6 were mixed, cured, and characterized forthermal conductivity in an identical manner as described in Example 1.

Selection of base filler chemistry is another parameter influencing theultimate conductivity observed in in situ derived heterogeneouscomposites. Table 5 shows the three examples of heterogeneous compositesbased on pure silver, silver coated copper, and aluminum flake. Each ofthe fillers possesses a similar stearic acid coating. Comparing thethermal conductivity of each Example on an equal volume percent fillerbasis to that of the homogeneous (conventional) composite containingsilver flake gives an indication of the extent of sample heterogeneityand level of particle sintering.

Example 5-A exhibits over a three fold improvement in thermalconductivity relative to the homogeneous system at a fillerconcentration of 5 volume percent. Example 5-B, based on silver coatedcopper, has a thermal conductive that is over two times that of thehomogeneous composites at filler loading 6 volume percent. Lastly,Example 5-C based on aluminum flake, exhibits a thermal conductivityabout 79% higher than that of the homogeneous composite. The lowerconductivity of this heterogeneous, aluminum filled composite relativeto heterogeneous samples based on pure silver is a reflection of thealuminum's inability to sinter. Nevertheless, the aluminum-rich domainsformed are still enough to significantly increase thermal conductivity.

TABLE 5 Effect of filler type on the thermal conductivity ofheterogeneous composites Ingredient by Example Example Example wt % (vol%) Control 5-A 5-B 5-C DGEBF     8.27x 50.2 49.1 51.1 PAA — 17.1 16.717.4 DETA x — — — Silver Flake^((a)) 100-x 32.7 (5) — — Silver coatedcopper — — 34.2 (6) — flake^((b)) Aluminum flake^((c)) — — — 31.5 (16)Total 100 100   100   100   Cured Structure Homo- Hetero- Hetero-Hetero- geneous geneous geneous geneous Thermal Conductivity, See  1.07 0.83  1.07 k (W/m · K) FIG. 4/Table Ratio of k to k_(control)    1.0 3.2  2.3  1.79 at same vol % filler (See FIG. 4/Table 2)^((d))^((a))Stearic acid coating. ^((b))Silver amount = 20 wt %. Fatty acidcoating is present on the outer silver layer. ^((c))Fatty acid coating.^((d))Linear regression of the homogeneous data in Table 2 and FIG. 4results in k = 0.0241 *(vol % Ag) + 0.211 with a goodness of fit R² =0.96. This trend line provides a basis for comparison of thermalconductivity a homogeneous system (control) versus that of heterogeneoussystems (Examples 5-A, B and C).

EXAMPLE 6

Sample in Tables 6 and 7 were mixed, cured, and characterized inidentical manner described in Example 1.

Table 6 shows the effect amount of filler coating on the thermalconductivity of composites based on DGEBF (resin), PAA (curative), andcoated silver flake. The data is based on a common silver flake, yet theamount of stearic acid coating on the flake differs. As seen in Table 6,a low to medium coating level, i.e. less than a few monolayers result inexceptional thermal conductivity. However, an excessive coating amountleads to a substantial reduction in thermal conductivity.

The chemistry of the filler coating will also affect the level ofheterogeneity formed during curing and the corresponding composite'sproperties. Table 6 shows the influence of two different silver coatingson the thermal conductivity of composites based on DGEBF, PAA, andsilver flake. The data is based on the same base silver flake withequivalent amounts of filler coating. The use of an ester acid coatingon the silver results in lower composite thermal conductivity than usinga long chain unsaturated fatty acid coating. However, the heterogeneouseffect in the cured composite is still evident.

TABLE 6 The effect of filler coating amount on the thermal conductivityof heterogeneous composites containing fatty acid coated silver flakefilled (33 vol %). Coating Thermal Amount Conductivity, k Example^((a))(mg/m²)^((b)) (W/m · K) A-6 Low 25.6 B-6 Med 23.0 C-6 High 13.7^((a))Hetergeneous composites were formed from the reaction DGEBF(resin) and PAA(curative) in the presence of the silver flake. ^((b))Theflakes differ only in the amount of fatty acid coating.

TABLE 7 The effect of coating chemistry on the thermal conductivity ofsilver flake filled (25 vol %) DGEBF composites cured with PAA. CoatingType Filler surface Coating Thermal on Silver area Amount Conductivity,k Example Flake (m²/g) (mg/m²)^((a)) (W/m · K) A-7 Long chain 0.71 4.7814.0 unsaturated fatty acid B-7 Ester acid 0.66 4.24 10.9^((a))Determined by the ratio of filler surface area to that of theweight loss (mg organic/g silver) at 538° C. in air.

EXAMPLE 7

Samples in Table 8 and FIG. 10 were mixed (uncured state) andcharacterized as outlined in Example 1. Each uncured sample was castbetween 19 mm thick, Teflon coated aluminum plates separated with 1 mmglass slides as spacers. The Control, Examples 7-A and 7-B were curedwith a convection oven using a programmed ramp which consisted ofheating the sample from room temperature to 160° C. over the course of40 minutes followed by an isothermal hold for 1 hour. Example 7-C wascured by heating the sample in a convection oven from room temperatureto 200° C. (heating rate of approximately 40° C./min) and held at 200°C. The total cure time was 3 hours.

The chemical structure of organic components is another parameteraffecting the extent heterogeneity in the structure formed during cureand the properties of the resulting composite. Table 8 provides examplesof different types of resins (organic components) that produceheterogeneous structures when cured with PAA in the presence of stearicacid coated silver flake. A control sample possessing a homogeneousmorphology provides a basis for reference. The thermal conductivity ofheterogeneous examples relative to that of the control give anindication of extent of heterogeneity in composite structure uponcuring. DGEBF when cured with PAA in the presence of silver results inabout a 22 fold higher thermal conductivity relative to the homogeneoussystem. Similarly, an epoxy novolac cured with PAA results in a 16 folddifference in thermal conductivity relative to the homogeneouscontaining identical level (volume basis) of silver flake. Lastly,curing an ethoxylated bisphenol A diacrylate with PAA via a Michael'saddition reaction results in a composite having over 6 times higherconductivity than that of the control. The SEM photomicrograph ofExample 7-C shows that the heterogeneous structured during cure. As withpreviously in Example 1, the heterogeneous structure comprises discretepolymer rich domains (very light, globular regions) distributedthroughout a continuous silver-rich phase.

TABLE 8 Heterogeneous structures from alternative resins Ingredient byExample Example Example wt % (vol %) Control 7-A 7-B 7-C DGEBF     8.27x13.4 — — Epoxy novalac — — 18.1 — Ethoxylated — — — 13.0  bishpenol Adiacrylate PAA —  4.6  6.9 4.8 DETA x — — — Silver flake^((a)) 100-x82.0 (33) 75.0 (25) 82.2 (33) Total 100 100   100   100   CuredStructure Homo- Hetero- Hetero- Hetero- geneous geneous geneous geneousThermal See 22.3 13.1 6.5 Conductivity, k FIG. 4 (W/m · K) Ratio of k tok_(control)    1.0 22  16  6.4 at same vol % Ag (See FIG. 4)^((b))^((a))Stearic acid coated silver flake (surface area = 0.83 m²/g, weightloss in air at 538° C. = 0.35%) ^((b))Linear regression of thehomogeneous data in Table 2 and FIG. 4 results in k = 0.0241 *(vol %Ag) + 0.211 with a goodness of fit R² = 0.96. This trend line provides abasis for comparison of thermal conductivity a homogeneous system(control) versus that of heterogeneous systems (Examples 7-A, B and C).

Although the present invention has been described with reference toparticular embodiments, it should be recognized that these embodimentsare merely illustrative of the principles of the present invention.Those of ordinary skill in the art will appreciate that thecompositions, apparatus and methods of the present invention may beconstructed and implemented in other ways and embodiments. Accordingly,the description herein should not be read as limiting the presentinvention, as other embodiments also fall within the scope of thepresent invention as defined by the appended claims.

1. A method for producing a composite comprising: a) selecting areactive organic compound; b) selecting an inorganic filler component;c) mixing the reactive organic compound and the inorganic fillercomponent, wherein at room temperature the organic compound and thefiller component mix to form a substantially homogeneous structurehaving a bulk filler concentration; and, d) reacting the organiccompound to form a polymer; wherein the polymer has a repulsiveinteraction with the inorganic filler thereby creating, in situ, aheterogeneous structure comprising filler rich domains.
 2. The method ofclaim 1, wherein the concentration of the filler is higher than that ofa bulk filler concentration.
 3. The method of claim 1, wherein thereactive organic compound comprises at least one of monomers, oligomers,prepolymers, or reactive polymers.
 4. The method of claim 3, wherein theorganic compound further comprises a cure agent.
 5. The method of claim1, wherein the reaction of step d) is advanced by heating the mixture.6. The method of claim 1, wherein the reaction of step d) is advanced byexposing the mixture to activating ultraviolet radiation.
 7. The methodof claim 1, further comprising a second filler component.
 8. The methodof claim 7, wherein the second filler component resides substantiallywith the polymer after the organic compound has been reacted.
 9. Themethod of claim 1, wherein the inorganic filler component comprises aninorganic filler coated with an organic coating.
 10. The method of claim9, wherein the organic coating on the filler has an affinity for thereactive organic compound.
 11. The method of claim 9, wherein thecoating on the filler comprises stearic acid.
 12. The method of claim 9,wherein the coating on the filler is present in a single layer asaveraged over substantially all of the filler.
 13. The method of claim9, wherein the organic coating on the filler has a repulsive interactionwith the new polymer formed from the step of reacting the organiccomponent.
 14. The method of claim 9, wherein the coating on the fillercomprises a non-polar coating.
 15. The method of claim 1, wherein thepolymer formed during step d) comprises polar moieties.
 16. The methodof claim 1, wherein the filler is thermally conductive.
 17. The methodof claim 1, wherein the filler is electrically conductive.
 18. Themethod of claim 1, wherein the filler comprises solder.
 19. The methodof claim 1, wherein the filler comprises less than 75 percent by weightbased on the total weight of the composition.
 20. The method of claim 1,wherein the filler comprises less than 50 percent by volume based on thetotal volume of the composition.
 21. The method of claim 1, wherein thefiller comprises at metallic filler of at least one of nickel, copper,silver, palladium, platinum, gold, and alloys thereof.
 22. The method ofclaim 1, wherein the filler comprises a cold worked silver flake. 23.The method of claim 1, wherein the filler comprises a sinterable filler.24. The method of claim 23, further comprising the step of sintering thefiller particles together.
 25. The method of claim 24, wherein the stepof sintering the filler particles together and the step of reacting theorganic compound are performed simultaneously.
 26. The method of claim23, wherein substantially all of the sinterable filler particles thatare in direct contact with one another are sintered.
 27. The method ofclaim 24, wherein the step of sintering is performed at a temperatureabove approximately 100° C.
 28. The method of claim 24, wherein the stepof sintering is performed at a temperature of above approximately 150°C.
 29. The method of claim 24, wherein the sintering step is enhanced byan applied pressure on the composition.
 30. The method of claim 24,wherein the degree of sintering is regulated through selection ofsintering temperature and pressure.
 31. The method of claim 1, whereinthe mixture of the reactive organic component and the filler is asolvent-free 100% solids composition.